Wireless phone providers are developing dual mode phones that have the functionality to communicate with a cellular network and another type of wireless data network. The cellular network is generally a 2G or 3G network that includes a circuit-switched core network (e.g., UMTS or cdma2000) for voice communications, and may also include a packet-switched core network (e.g., GPRS) for data communications. The wireless data network is generally a 3G or 4G data-only or data-optimized network typically used for data communications, such as Internet browsing, email, Voice over IP (VoIP), online gaming, etc. The concept of the dual mode phone is to allow a user the flexibility to communicate with either the cellular network or the wireless data network.
When a dual mode phone is in range of the cellular network, the dual mode phone registers with the cellular network to receive communication access. Network elements in the cellular network may then serve the dual mode phone to provide service. For example, a Mobile Switching Center (MSC) or a Serving GPRS Support Node (SGSN) may serve a dual mode phone while it is registered with the cellular network, and act as serving elements for the phone.
In addition to cellular networks, dual mode phones may come into range of local wireless “hot spots” in a corporation or enterprise, airports, book stores, coffee shops, etc. The wireless hot spot may be in a building where cellular service is unavailable or may overlap a cellular service area. When a dual mode phone is in range of a wireless hot spot, the dual mode phone registers with a packet-switched core network via the Wireless LAN (WLAN) to receive communication access. Some examples of a packet-switched core networks are an IP Multimedia Subsystem (IMS) network and a Long Term Evolution/Evolved Packet Core (LTE/EPC) network. Network elements in the packet-switched core network may then serve the dual mode phone to provide services. For example, a Mobility Management Entity (MME) and a Packet Data Network Gateway (PDN-GW) may serve a dual mode phone while it is registered with the packet-switched core network, and act as serving elements for the phone.
The packet-switched core network includes a subscriber server, such as a Home Subscriber Server (HSS), that is a master database for storing subscriber profiles, performing authentication and authorization of the user, and providing information about the physical location of the user. The packet-switched core network may also include or communicate with application servers (AS), which are configured to provide particular services for the dual mode phone. The application servers communicate with the HSS over a Diameter Sh interface to extract the necessary service data to dispatch the logic of a service.